Stephen Schneider’s climatechange.net is a critical component of Steve’s legacy, and is an outreach tool about which Steve cared deeply. He saw this website as way to effectively speak to diverse groups who are crucial to countering the misinformation campaigns of special interests and ideologues as well as developing and implementing effective climate policies: the media, the community of disciplinary scientists, decision makers at local, state, national and international levels, the faith communities, celebrities committed to supporting change, and corporate executives in key industries as well as the public—informing all of us of the latest findings and the risks we face, and inspiring us to continue to learn more and take action. And just as important, Steve was profoundly dedicated to influencing, impacting, and developing the next generation of climate scientists and policy makers through his teaching and outreach, as his many students will attest. The words mentor and friend are used together by so many that one wonders how one person could have so much impact on so many lives.

Steve hoped that this website would be useful to all interested in the interdisciplinary science of climate change. As he said, this site is a work in progress — an in-depth mini-book with links to related websites and relevant literature, placed in a context that was his view of the climate problem.

We are currently updating climatechange.net with new and updated content in his words that he wanted to have posted as well as reflections by people he taught.

Please explore and come back often as this dynamic site evolves.

Throughout human history, climate has both promoted and
constrained human activity. In fact, humans only very recently have been able
to substantially reduce the degree to which they are affected by climate variability,
mainly through advances in technology and the development of more sophisticated
infrastructure. For example, high-yield agriculture and efficient food distribution
and storage systems have virtually eliminated famine in most countries with
developed or transitioning economies.

On the other hand, human activity can and has also affected
the climate. From Swedish scientist Arrhenius' 1896 study of how changes in
carbon dioxide (CO2) could affect climate, to English engineer G.S.
Callendar's assertion in 1938 that a warming trend caused by increases in CO2 was underway, to Massachusetts Institute of Technology scientist Lorenz's
suggestion at a 1965 conference in Boulder, CO, that climate change could cause
catastrophic "surprises", to the establishment of the Intergovernmental
Panel on Climate Change (IPCC) in 1988, support has increased for the
idea that there exists a complex, and perhaps dangerous, society-nature cycle:
climate influences human activities that, in turn, influence climate, etc. (For
much more information on the history of climate change research, see Spencer
Weart's website, The
Discovery of Global Warming.)

Figure
— Details
of Earth's energy balance (source: Kiehl
and Trenberth, 1997). Numbers are in watts per square meter of Earth's
surface, and some have a range of uncertainty of as much as +/- 20%. The greenhouse
effect is associated with the absorption and re-radiation of energy by atmospheric
greenhouse gases and particles, which results in a downward flux of infrared
radiation from the atmosphere to the surface (back radiation) and therefore,
a higher surface temperature. Note that the total rate at which energy leaves
Earth (107 W/m2 of reflected sunlight plus 235
W/m2 of infrared [long-wave] radiation) is equal
to the 342 W/m2 of incident sunlight. Thus, Earth
is in approximate energy balance in this analysis.

"As
the climate continues to change —and in most mainstream scientific
studies, change is expected to accelerate substantially during the twenty-first
century— we can expect natural systems to become highly stressed."

However, climate change didn't jump onto the global public's
radar screen, politicians, and the media as an important issue until 1995, when
the IPCC first announced in Working Group I's contribution to the Second
Assessment Report, or SAR (which was released in final form in 1996),
that "the balance of evidence suggests that there is a discernible human influence
on global climate." The record high temperatures in the last few decades (see
a 2003 article
in The Guardian), with 1998, 2002, and 2003 being the warmest years on record,
as well as dramatic increases in storm damage between the 1960s and 1990s, have
lent credibility to the IPCC’s finding (see a Trend
Graph from the IPCC and a similar figure
from page 4 of a presentation given by Ray Bradley; original Mann
et al., 2003). Then, in its Third
Assessment Report (TAR) in 2001, the IPCC estimated that by 2100, the
planet would warm by between 1.4 °C and 5.8 °C, up from the range of
1.0 °C to 3.5 °C that had been estimated in the SAR. While warming
at the low end of this range, of say 1.5 °C, would likely be relatively
adaptable for most human activity, it would still be significant for some “unique
and valuable systems.” Warming of 6 °C could have widespread catastrophic
consequences, as a temperature change of 5 to 7 °C on a globally
averaged basis is about the difference between an ice age and an interglacial
period. The 2001 IPCC assessment both reinforced the original (1996) claim of
detection of an anthropogenic climate signal and brought to the forefront a
new “discernible” statement — this time that recent observations
of wildlife, marine systems, ice layers, and the timing of vegetation lifecycles
suggest that there now appears to be a discernible impact of regional climatic
variations on natural systems (see
IPCC Working Group II Report and Root/Schneider:Wildlife
Responses to Climate Change: Implications). The prime implication of
this new finding is that as the climate continues to change —and in most
mainstream scientific studies, change is expected to accelerate substantially
during the twenty-first century— we can expect natural systems to become
highly stressed.

"“End
of the world” and “good for the Earth” are, in my experience,
the two lowest probability cases."

Special interest groups followed the IPCC proceedings closely.
Given the broad range of possible outcomes, proponents of the many sides of
the climate change debate (often dichotomized into “ ignore the problem
” versus “stop it ” camps, though it is actually an issue
with many, many sides) deliberately selected and continue to select information
out of context that best supports their ideological positions and their or their
clients' interests. They frequently practice a phenomenon I call
"courtroom epistemology": refusing to acknowledge that an issue (climate
change, in this case) is multifaceted, and presenting only their own arguments,
ignoring opposing views. Deep ecology groups point to the most pessimistic outcomes,
using their warnings of climate catastrophe to push for the creation and implementation
of energy taxes, abatement policies, and renewable energy promotion and subsidies
(as many believe renewable energy is “the solution). Clearly, such policies
would affect the industries that produce and use the most energy, especially
the oil and auto industries. The auto, oil, and other fossil fuel-intensive
industry groups, uncoincidentally, tend to be the extreme optimists in the global
warming debate though, ironically, they often are the pessimists when it comes
to estimating the costs of fixing the problem. They attempt to trivialize the
potential hazards of climate change and focus on the least serious outcomes
and the most expensive mitigation policies to discourage political action.

This plays into the media's tendency to engage in "balanced"
reporting: polarizing an issue (despite its being multifaceted) and making each
"side" equally credible. The media dutifully report the dueling positions of
ecology and industry, further confusing policymakers and the public with an
endless parade of op-eds and stories quoting those suggesting that global warming
is either “good for the Earth and too expensive to fix anyway” or
“the end of the world but nonetheless
relatively cheap to solve with solar or wind power.” “End
of the world” and “good for the Earth” are, in my experience,
the two lowest probability cases (as are "it would bankrupt us to mitigate
climate changes" and "technology will solve climate change at no cost").
Neither side usually offers probabilities of such outcomes.

"Just
because we scientists have Ph.D.s we should not hang up our citizenship
at the door of a public meeting."

Eliminating this confusion and misrepresentation of the
climate change debate requires the participation of scientists, citizens, and
journalists alike. First, scientists should not be discouraged on principle
to enter the public debate on climate change both as scientist-advocates
and scientist
popularizers; if they don't, popularization of potential probabilities
and consequences of climate change will occur without their input and will likely
be more inaccurate. A scientist should also transcend prejudices against non-frequentist
(i.e., subjective) analysis and treat climate change like the issue that it
is: one for which future empirical data cannot be obtained (as it is simply
impossible to obtain hard data for events occurring in the future) and which
therefore necessitates the use of Bayesian, or subjective, probabilities
and projections/models — our 'cloudy crystal balls' — that compile
all the information we can possibly bring to bear on the problem, including,
but not limited to, direct measurements and statistics. It is scientists, not
policymakers, who should provide subjective probabilistic assessments of climate
change. Just because we scientists have Ph.D.s we should not hang up our citizenship
at the door of a public meeting  we too are entitled to advocate personal
opinions, but we also have a special obligation to make our value judgments
explicit. If they do express opinions, scientists should attempt to keep their
value judgments out of the scientific assessment process but should make
their personal values and prejudices clear regardless. It is then the role of
the scientist-popularizer to propagate and promote these assessments and values
in an understandable manner in the public realm so that the scientific community's
findings and the scientist's ideas are heard and his/her suggestions are available.
An effective scientist-popularizer must balance the need to be heard (good sound
bites) with the responsibility to be honest (see "the
double ethical bind pitfall") as well. Doing both is essential.

Citizens must demand that scientists provide honest, credible
assessments that answer the "three questions of environmental literacy":
1) What can happen?; 2) What are the odds of it happening?; and 3) How are such
estimates made? Citizens must also achieve a certain level of environmental,
political, and scientific literacy themselves so that they feel comfortable
distinguishing climate change fact from fiction and making critical value judgments
and policy decisions, in essence becoming "citizen
scientists". Just as popularization of potential probabilities
and consequences will occur with or without input from scientists, policy decisions
will be made with or without input from an informed citizenry. I hope that citizens
will take responsibility for increasing their scientific, political, and environmental
literacy and recognize the importance of the positive effect that an informed
public will have on the policy process.

Citizens and scientists clearly can't operate as completely
separate entities in the climate change debate. Their interaction is essential,
especially when it comes to "rolling
reassessment". Given the uncertain nature of climate change, citizens
and scientists should work together to initiate flexible policies and management
schemes that are revisited, say, every five years. The key word here is flexible.
Knowledge is not static — there are always new outcomes to discover and
old theories to rule out. New knowledge allows us to reevaluate theories and
policy decisions and make adjustments to policies that are too stringent, too
lax, or targeting the wrong cause or effect. Both scientist-advocates and citizen-scientists
must see to it that once we’ve set up political establishments to carry
out policy that people do not become so vested in a certain process or outcome
that they become reluctant to make adjustments, either to the policies or the
institutions.

"Citizens
should make sure that the public debates take into account all knowledge
available on climate change."

In addition, citizens and scientists must coordinate with
journalists and other media figures to ensure accuracy in the media portrayal
of climate change (see The
Journalist-Scientist-Citizen Triangle). We scientists need to take more
proactive roles in the public debate. We need to help journalists by agreeing
to participate in the public climate change debate and by using clear metaphors
and ordinary language once we do so. We should go out of our way to write review
papers from time to time and to present talks that stress well-established principles
at the outset of our meetings. Before we turn to more speculative, cutting-edge
science; we should deliberately outline the consensus before
revealing the contention. Citizens should make sure that the public
debates take into account all knowledge available on climate change. Hopefully,
their actions will encourage reporters to replace the knee-jerk model of "journalistic
balance" with a more accurate and fairer doctrine of "perspective":
one that communicates not only the range of opinion, but also the relative credibility
of each opinion within the scientific community. (Fortunately, most sophisticated
science and environment reporters have abandoned the journalistic tradition
of polarization of only two "sides", but nevertheless, especially in the political
arena, such falsely dichotomous "balance" still exists).

To further clarify the climate change issue, we must consider
its three main components: Climate Science, Climate Impacts, and
Climate Policy (see below).

The climate change debate is characterized by deep uncertainty,
which results from factors such as lack of information, disagreement about what
is known or even knowable, linguistic imprecision, statistical variation, measurement
error, approximation, subjective judgment on the structure of the climate system,
among others (see Decision
Making Under Uncertainty). These problems are compounded by the global
scale of climate change, which produces varying impacts at local scales, long
time lags between forcing and its corresponding responses, very long-term
climate variability that exceeds the length of most instrumental records, and
the impossibility of before-the-fact experimental controls or empirical observations
(i.e., there is no experimental or empirical observation set for the climate
of, say, 2050 AD, meaning all our future inferences cannot be wholly “objective,”
data-based assessments — at least not until 2050 rolls around). Moreover,
climate change is not just a scientific topic but also a matter of public and
political debate, and degrees of uncertainty and various claims and counterclaims
may be played up or down (and further confused, whatever the case) by stakeholders
in that debate (see Post-Normal
Science).

"In
the past few centuries, atmospheric carbon dioxide has increased by
more than 30 percent, and virtually all climatologists agree that the cause
is human activity, predominantly the burning of fossil fuels and, to a considerable
extent, land uses such as deforestation. "

However, it is important to understand thatthe greenhouse
phenomenon is well-understood and solidly grounded in basic science(see
Climate
Science). It is scientifically well-established that the
Earth's surface air temperature has warmed significantly, by about 0.7°C
since 1860, and that an upward trend can be clearly discerned by plotting historical
temperatures. Such a graph
would show a rapid rise in temperature at the end of the twentieth century.
This is supported by the fact that all but three of the ten warmest years on
record occurred during the 1990s. In addition, it is well-established that human
activities have caused increases in radiative forcing, with radiative forcing
defined as a change in the balance between radiation coming into and going out
of the earth-atmosphere system. In the past few centuries, atmospheric
carbon dioxide has increased by more than 30 percent, and virtually all climatologists
agree that the cause is human activity, predominantly the burning of fossil
fuels and, to a considerable extent, land uses such as deforestation.

More controversial is the extent to which humans have and
are contributing to climate change. How much of global warming up to this point
has been natural versus anthropogenically-induced, and by how much will humans
and natural changes in the Earth each contribute to future disturbance? The
IPCC has attempted to tackle this in its Special
Report on Emission Scenarios (SRES), which contains a range of possible
future emissions scenarios based on different assumptions regarding economic
growth, technological developments, and population growth, arguably the three
most critical determinants of future climate change. These have been used to
project the increases in CO2 concentrations (and other radiative
constituents) out to 2100, and it is hoped that they will help policymakers
weigh action to stem potentially devastating consequences in the future. (For
more information, see Scenarios).

These and other climate change projections depend on detailed
modeling. The most consistent way scientists codify our knowledge is by constructing
models made up of the many subcomponents of the climate system that reflect
our best understanding of each subsystem. The system model as a whole cannot
be directly verified before the fact — that is, before the future arrives
— but it can be tested against historical situations that resemble aspects
that we believe will occur in the future (see Climate
Modeling). The most comprehensive models of atmospheric conditions are
three-dimensional, time-dependent simulators known as general circulation models
(GCMs) — see Climate
Science. The most useful GCMs are those that also project "surprise"
events, and are able to test emissions scenarios that can avoid such surprises.

While modeling has become both more complex and more accurate
as computing abilities have advanced and more is understood about the climate
problem, scientists still have to deal with an enormous amount of uncertainty,
as mentioned above. In climate modeling, one major unknown is climate
sensitivity, the amount by which the global mean temperature will increase
for a doubling of CO2 concentrations. Many
scientists have done extensive empirical and modeling research on this subject,
and most have found that most climate sensitivity estimates fall somewhere within
the IPCC's range of 1.5-4.5 °C. However, more
recently some have estimated it could be lower than 1.5 °C or it could be an alarming 6 °C or higher (see Karl
and Trenberth, 2003). (Remember that a 5-7 °C drop in temperature is all that separates Earth’s present
climate from an ice age).

Figure —
Reasons for concern about climate
change impacts(source:
IPCC WG 2 TAR,figure
SPM-2). The left part of the figure displays the observed temperature
increase up to 2000 and the range of projected increases after 2000 as estimated
by IPCC,
WG I (IPCC, 2001a) for scenarios from the Special Report
on Emission Scenarios (SRES
— see the Emission
scenarios). The right panel displays conceptualizations of
five reasons for concern regarding climate change risks evolving through 2100.
White indicates neutral or small negative or positive impacts or risks, yellow
indicates negative impacts for some systems, and red means negative impacts
or risks that are more widespread or greater in magnitude. This figure shows
that the most potentially dangerous impacts (the red colors on the figure)
typically occur after a few degrees warming — thus, my later use of
3.5 °C as a tentative “threshold”
for serious climate damages is very conservative. The risks of adverse impacts
from climate change increase with the magnitude of climate change.

It is important that scientists continue to develop more
credible models and probe the issue of climate sensitivity, as improvements
in the science will lead to improvements in our understanding of the potential
impacts of various levels of temperature change. Despite uncertainties
surrounding sensitivity, the IPCC has projected that, if its latest estimate
that on a global average basis, the Earth's atmosphere near the surface will
warm somewhere between 1.4 and 5.8 °C by 2100
is correct, likely effects will include: more frequent heat waves (and less
frequent cold spells); more intense storms (hurricanes, tropical cyclones, etc.)
and a surge in weather-related damage; increased intensity of floods and droughts;
warmer surface temperatures, especially at higher latitudes; more rapid spread
of vector-borne disease; loss of farming productivity in warm climates and movement
of farming to other regions, most at higher latitudes; rising sea levels, which
could inundate coastal areas and small island nations; and species extinction
and loss of biodiversity (see table - Projected
effects of global warming). Schneider,
Kuntz-Duriseti, and Azar (2000)have argued that the best way to estimate
the full extent of such damages comes from examining not just quantifiable monetary
("market") damages, but several metrics, termed the "five
numeraires": monetary loss (market category), loss of life, quality
of life (including coercion to migrate, conflict over resources, cultural diversity,
loss of cultural heritage sites, of hunting grounds, etc.), species or biodiversity
loss, and distribution/equity. Use of multiple metrics should ensure a fairer,
more comprehensive assessment of the actual benefits of avoiding global warming.

"Policymakers
are better able to determine what is 'dangerous' and formulate effective
legislation to avoid such dangers if probabilities appear alongside scientists'
projected consequences."

Estimating climate damages that are expected to occur gradually
and their effects is simple relative to forecasting "surprise" events and their
consequences (see Climate
Surprises). The IPCC and others have stated that "dangerous" climate
change, including surprises, could occur, especially with more than a few degrees
Celsius of additional warming. Surprises, better defined as imaginable abrupt
events, could include deglaciation or the alteration of ocean currents (the
most widely-used example of the latter being the collapse of the Thermohaline
Circulation, or THC, system in the North Atlantic). Rather than being ignored,
surprises and other irreversibilities like species extinctions should be treated
like other climate change consequences by scientists performing risk assessments,
where risk is defined as probability x consequence.
The probability component of the risk equation will entail subjective judgment
on the part of scientists, but this is far preferable to avoiding the risk equation
entirely. Policymakers are better able to make a judgment about what is "dangerous"
and formulate effective actions to avoid such dangers when probabilities appear
alongside scientists' projected consequences.

These probabilities and consequences will vary regionally
(see Regional
Impacts). In general, temperature rises are projected to be greatest
in the subpolar regions, and to affect the winter more dramatically than the
summer. Hotter, poorer nations (i.e., developing nations near the equator)
in the political "South" are expected to suffer more dramatic effects
from climate change than their cooler developed neighbors in the political "North".
This is partly due to the lower expected adaptive capacities of future societies
in developing nations when compared with their developed-country counterparts,
which in turn depend on their resource bases, infrastructures, and technological
capabilities. This implies that impacts may be asymmetrically felt across the
developed/developing country divide. The scenario in which climate change brings
longer growing seasons to the rich northern countries and more intense droughts
and floods to the poor tropical nations is clearly a situation ripe for increasing
North-South tensions in the twenty-first century, especially since the economic
benefits of using the atmosphere as a "dump" for our tailpipes is
disproportionately in favor of the wealthy.

"All
people, governments, and countries should realize that 'we're in this together'."

Regardless of the different levels of vulnerability and
adaptive capacity that future societies are expected to have and the need for
regional-level assessments, all people, governments, and countries
should realize that "we're in this together". In all regions, people's actions
today will have long-term consequences. Even if humanity completely abandons
fossil fuel emissions in the 22nd century, essentially irreversible
long-term concentration increases in CO2 are projected to remain
for centuries or more. Thus, the surface climate will continue to warm from
this greenhouse gas elevation, with a transient response of centuries before
an equilibrium warmer climate is established. How large that equilibrium temperature
increase is depends on both the final stabilization level of the CO2
and the climate sensitivity. One threat of a warmer climate would be an ongoing
rise in sea level. Warmer atmospheric temperatures would lead to warmer ocean
water (and corresponding volumetric expansion) as the heat becomes well-mixed
throughout the oceans — a time known to be on the order of 1,000 years.
Instead of only up to a meter of sea level rise over the next century or two
from thermal expansion — and perhaps a meter or two more over the five
or so centuries after that as the warming penetrates all depths of the ocean
— significant global warming could very well trigger nonlinear events
like a deglaciation of major ice sheets near the poles. That would cause many
additional meters of rising seas for many millennia, and once started might
not be reversible on the time scale of thousands of years (see figure - CO2
concentration, temperature and sea level). Thus, the behavior of only a
few generations can affect the sustainability of coastal and island regions
for a hundred generations to come.

"The
decision on whether to take actions on climate change entails a value judgment
on the part of the policymaker regarding what constitutes "dangerous" climate
change, ideally aided by risk assessments provided by scientists."

In the face of such uncertainty, potential danger, and long-term
effects of present actions, how should climate change policy be approached?

Climate change and almost all interesting socio-technical
problems with strong stakeholder involvement fall into the post-normal
science categorization: they are riddled with “deep uncertainties”
in both probabilities and consequences that are not resolved today and may not
be resolved to a high degree of confidence before we have to make decisions
regarding how to deal with their implications. With imperfect, sometimes ambiguous,
information on both the full range of climate change consequences and their
associated probabilities, decision-makers must decide whether to adopt a "wait
and see" policy approach or follow the "precautionary principle" and hedge against
potentially dangerous changes in the global climate system. Since policymakers
operate on limited budgets, they must determine how much to invest in climate
protection versus other worthy improvement projects — e.g., new nature
reserves, clean water infrastructure, or education.

Ultimately, the decision on whether to take actions on climate
change entails a value judgment on the part of the policymaker regarding what
constitutes "dangerous" climate change, ideally aided by risk assessments provided
by scientists. These risk assessments can be enhanced by explanations of integrated
assessment models (IAMs), which are important tools for studying the impacts
of climate change on the environment and society (see Climate
Impacts), as well as the costs and benefits of various policy options
and decisions (see Climate
Policy). As evidenced by interactions at international climate negotiations
and the different degrees to which climate change abatement and/or adaptation
policies have been adopted by different countries (see "Come
On, Everybody Else Is Doing It"), not all policymakers' value judgments
are equal.

"The
most robust policy strategies are often those which provide “ancillary
benefits..."

While a decision-maker must make the final decision on policy,
many scientists have encouraged the "better safe than sorry" approach and have
advocated the practice of hedging: initially slowing down our impacts on the
climate and then adopting flexible policies that can be updated as future climate
conditions occur and are better understood. As Christian Azar and I (Schneider
and Azar, 2001) mentioned: "In our view, it is wise to keep many doors
— analytically and from the policy perspective — open. This includes
acting now so as to keep the possibility of meeting low stabilization targets
open. As more is learned of costs and benefits in various numeraires and political
preferences become well developed and expressed, interim targets and policies
can always be revisited." In addition to being based on "rolling
reassessment", as described in the quote above, the most robust policy
strategies are often those which provide “ancillary benefits” —
that is, policies which help to solve more than one problem at once. (See Climate
Policy). For example, reducing the unfiltered burning of coal, which
is highly polluting, in crowded cities like New Delhi and Beijing by replacing
it with more efficient, less polluting natural gas power sources not only reduces
the emissions of greenhouse gases that cause climate change, but also reduces
the conventional “criteria” air pollutants that are well-known to
adversely affect human health (see the EPAand Harvard
School of Public Health websites on air pollution hazards to health).

Cost-benefit
analyses (CBAs) are also useful in deciding the ifs and whats of climate
change policy, but uncertainties make this exercise difficult as well, especially
when attempting to estimate the costs of surprise and other catastrophic events.
A few economists have concluded that stringent measures to control emissions
of CO2 would be very costly even when the benefits of reducing the
emissions (i.e., avoided climatic changes) are taken into account, but many
others have found that much stronger cuts in emissions are defensible on economic
efficiency grounds alone. At present, it seems that CBAs applied to the problem
of global climate change can largely justify a wide range of emission reduction
targets, marginal or substantial. The latter will be particularly justifiable
if nasty surprises are taken into account.

"Encouraging
technological change through energy policies in particular is of critical
importance when addressing climate change."

Any policies that are implemented should provide incentives
for, and possibly even go so far as to subsidize, technological
change. Encouraging technological change through energy policies in
particular is of critical importance when addressing climate change. For example,
rapid early growth in alternative energy sources like wind and photovoltaic
(PV) technology largely depends on government efforts to build these markets
through subsidies. If/when the government supports such initiatives, they gain
mainstream popularity and encourage further private investments, oftentimes
above and beyond what the policy provides. On the other hand, if policy measures
are delayed, public acceptance will likely be delayed as well. If the world
decided to defer implementation of the Kyoto
Protocol for another twenty years, for instance, it is likely that private
and government research, development, and demonstration of carbon-efficient
technologies would drop rather than increase. An overview of the climate-energy-policy
debate (including a summary and critique of the Bush climate response) can be
found in Holdren
2003 (see also "Report
by the E.P.A. Leaves Out Data on Climate Change" and "The
Science and Politics of Global Climate Change: Does the Bush Administration
Think It Can Fool Mother Nature?").

Future international climate change agreements should certainly
consider the contributions of the developed (high per capita emissions) versus
developing (low per capita emissions) countries to climate change. Aubrey Meyer
of the Global Commons Institute
has long argued for the principle of "contraction and convergence." "Contraction"
entails the shrinking of the developed countries' "share" of CO2
and other greenhouse gas emissions. In Meyer's view, rich countries, who are
appropriating a disproportionate fraction of the atmospheric commons, need to
cut back their emissions and allow poorer countries to emit more and catch up.
Eventually, the two groups will "converge" at a level at which per capita
emissions will be equal across nations while at the same time meeting "climate
safe" emissions targets for the world as a whole (see "Trading
Up to Climate Security").

"Substantial
reductions of carbon emissions and several fold increases in economic welfare
are compatible targets."

For all countries, a main factor influencing implementation
of climate policy today is based on a clarification of the overall costs of
stabilizing atmospheric CO2 levels (see Political
Feasibility). More pessimistic economists generally find deep reductions
in carbon emissions to be very costly — into the trillions of dollars.
For instance, stabilizing CO2 in 2100 at 450 ppm (current level is
about 360 ppm) would, according to Manne
& Richels (1997), cost the world between 4 and 14 trillion USD (this
is the present value for the whole century). Other top-down studies report similar
cost estimates (see
IPCC 2001c, chapter 8), but we must note, paradoxically, that the results
of even the most pessimistic economic models support the conclusion that substantial
reductions of carbon emissions and several fold increases in economic welfare
are compatible targets. To support this, Christian Azar and I developed
a simple economic model and estimated the present value (discounted to 1990
and expressed in 1990 USD) of the costs to stabilize atmospheric CO2
at 350 ppm, 450 ppm, and 550 ppm to be 18 trillion USD, 5 trillion USD, and
2 trillion USD, respectively, assuming a discount rate of 5% per year (see
Azar & Schneider, 2002). Obviously, 18 trillion USD is a huge cost,
considering that the output of the global economy in 1990 amounted to about
20 trillion USD and is about 37 trillion in 2003. However, viewed from
another perspective, an entirely different analysis emerges: the 18 trillion
USD cost represents the present value of lost income over the next 100 years.
In the absence of emission abatement and without any damages from climate change,
GDP is assumed to grow by a factor of ten or so over the next 100 years, which
is a typical value used in long-run modeling efforts. If even the most stringent
target, 350 ppm, were pursued, the costs associated with it would only amount
to a delay of two to three years in achieving this tenfold increase in global
GDP in 2100. Meeting the 350 ppm CO2 stabilization target would imply
that global income would be ten times larger than today by April 2102 rather
than 2100 (the date at which the tenfold increase would occur for the no-abatement-policies
scenario). This trivial delay in achieving phenomenal GDP growth is replicated
even in more pessimistic economic models. These models may be very conservative,
given that most do not consider the ancillary environmental benefits of emission
abatement, among other shortcomings.

Further Information

Throughout this website, I will try to distinguish the
well-established components of the climate change debate, contrast them with
the speculative aspects (and the overly contentious media/political debate),
and ultimately put this problem in the context of so-called Integrated Assessment
(seeIntegrated
Assessment) of policy responses to the advent or prospect of global
warming. I will also provide hundreds of links to other websites and literature
that elaborate on various aspects of each of the many components of the debate,
and will be sure that most points of view — some diametrically opposed
to mine— are all represented. I will, of course, provide my own views
on discordant opinions and their contexts that seem at variance with the increasingly
concerned mainstream assessments that have emerged in the past decade (see “Mediarology”).
The critical role of uncertainty will be frequently highlighted. (See, e.g.,
“When
Doubt is a Sure Thing”, the
Moss-Schneider Guidance Paper and a Climatic
Change editorial on uncertainties). Finally, I suggest areas for
further consideration.

For more detailed Climate Change information, see the full sections on: